The present invention relates to a decorticating device or machine in general, and more particularly to a device for stripping husks from grains, which machine is commonly known as a husker.
Grain huskers of various constructions are already known and have found a widespread use in various fields of human endeavor, especially in mills, cereal-manufacturing plants, and the like. These machines are used for separating the husks of grains, such as, for instance, rice or barley, from the soft nuclei of those grains. Usually, these machines include a housing which has an upper inlet for the grain to be husked or decorticated, and a lower outlet for the products of the husking operation. Then, a pair of decorticating rollers is accommodated in the interior of the housing, one of the rollers being mounted on the housing for rotation about a stationary axis, while the other roller is movable relative to the first-mentioned roller as a result of its being mounted on a carrier which is pivotably mounted on the housing. The movably mounted roller is pressed with a predetermined force against the stationarily mounted roller, the rollers being driven in rotation by a motor which is equipped with a driving pulley, while each of the rollers has a driven pulley, an endless element, such as a belt, being trained about the driving pulley, the driven pulleys, and at least one idler pulley.
It will be appreciated that the husker, in order to be marketable and usable, will have to satisfy several requirements. Of course, the husker will have to have the required throughput and will have to satisfy the requirements as to the quality of the husking operation performed thereby. However, an important consideration to be borne in mind when constructing the husker is that the construction of the driving arrangement for driving the decorticating rollers is of a crucial importance inasmuch as the complexity of and the manufacturing and operating expenses involved in connection with this driving arrangement determine, more than anything else, the overall cost of this machine.
Among the conventional decorticating machines of this type, there is already known from the Swiss Pat. No. 326,591 a husker in which a driven pulley is mounted on each of the shafts of the two decorticating rollers. In this machine, an endless driving belt is trained about these two driven pulleys and about two tensioning and guiding pulleys the positions of both of which are variable, the endless driving belt being advanced by a motor. This conventional arrangement is disadvantageous in that the angle of contact of the driving belt with the driven pulley associated with the stationarily mounted decorticating roller is quite small, as a result of which there exists the danger of slippage of the driving belt. In view of the fact that, on the one hand, the decorticating rollers must have a certain position relative to one another in order to achieve an unproblematical decorticating operation and, on the other hand, the elastic decorticating layer of the rollers wears off quite rapidly, a frequent adjustment of the position of the movably mounted decorticating roller is required to assure the proper relative disposition of the decorticating rollers; hence, a frequent re-tensioning of the driving belt is also necessary. This is quite disadvantageous not only because the operator of the machine must spend a considerable amount of time on adjusting the position of the movably mounted roller and re-tensioning the driving belt, but also in view of the fact that the operator is required to possess a certain degree of skill and must be attentive during the readjustment and re-tensioning in order to be able to properly perform the above-mentioned operations.
A different machine of this type is know from the British Pat. No. 797,372 wherein an electromotor which is accommodated in the housing of the machine drives the stationarily mounted decorticating roller via a first endless driving belt, while the movable decorticating roller is driven in rotation by a second endless driving belt. In this machine, the movement of the second driving belt is derived from the movement of the shaft of the stationarily mounted decorticating roller. Even this machine is disadvantageous in that the angle of contact of the second driving belt with the pulley which is mounted for transportation with the movable decorticating roller is quite small, and in that the wear of the decorticating layers of the decorticating rollers must be frequently compensated for by adjusting the position of the movably mounted decorticating roller and by re-tensioning the second driving belt.
Similar disadvantages are also present in the husker which is disclosed in the German published patent application DT-OS No. 23 04 704 in which a driving belt which is set in motion by a motor is trained about the driven pulleys mounted on the respective shafts of the two decorticating rollers, about a tensioning pulley, a guiding pulley and a driving pulley associated with the motor. Even in this machine, the driving belt contacts the driven pulleys associated with the decorticating rollers, the driving pulley and even the guiding pulley only to a small extent, and the tensioning pulley must be manually adjusted as to its position in dependence on the wear of the decorticating layer of the respective decorticating rollers, at frequent intervals, in order to assure that the driving belt has the necessary tension, which is particularly important in this machine in order to assure that a sufficient frictional resistance transmission is obtained at the minimum angle of contact of the driving belt with the respective pulleys.
A further conventional husker has been revealed in the published German patent application DT-OS No. 22 36 676 in which the driving arrangement includes a gear transmission incorporating three meshing gears, a first gear of this gear transmission being driven in rotation by an electric motor, a second of these gears driving the movable decorticating roller via a first belt drive, and the third gear driving the stationarily mounted decorticating roller via a second belt transmission which is controlable as to its speed. The two separate belt transmissions for the two decorticating rollers have advantageous angles of contact with their respective pulleys. Furthermore, when the position of the movable decorticating roller is changed on account of the wear of the decorticating layers of the decorticating rollers, it is not necessary to retension the driving belt which drives the movable decorticating roller. In view of this, this conventional machine is quite advantageous as to its function. However, this satisfactory function is achieved only at a relatively high material and manufacturing expense. In addition thereto, this machine is also disadvantageous in that it is not maintenance-free, which is a particular disadvantage especially when it cannot be assured that skilled maintenance personnel will be available whenever needed.
A husker of the German published patent application DT-OS No. 26 12 349 is another of the conventional machines of the type here under consideration, which includes a housing, two rollers which are mounted in the housing at a distance from each other and in mutual parallelism, a main shaft which carries one of the rollers and which is mounted in the housing for turning about a stationary axis, and a countershaft which carries the other roller and is supported in the vicinity of the free end of an arm which, in turn, is mounted on a base plate by means of a rotating axle which extends at a distance from and parallel to the stationary axis so that the countershaft can be moved with respect to the main shaft toward and away from the latter while the two shafts remain parallel to each other. The rotating axle is mounted in the housing in a predetermined relative position thereof with respect to the part of the countershaft which carries the respective roller. The arm which is pivotably movable about the rotating axis either above or below, supports only the removable decorticating roller and its driven pulley, while all other driving, driven, tensioning or guiding pulleys as well as the driving motor are arranged at fixed locations of the housing. The positional readjustment of the movable decorticating roller, which is necessitated by the unavoidable wear of the decorticating layers of the decorticating rollers, is here achieved manually by means of a handwheel, and the necessary retensioning of the endless driving belt is achieved by displacing the motor together with its driving pulley by means of an adjusting arrangement and a pivotably mounted carrier plate for the motor. Thus, the operator of even this machine must readjust not only the position of the movable mounted decorticating roller, but also the tension of the driving belt at frequent intervals and in dependence on the degree of the wear of the decorticating layers of the decorticating rollers, in order to assure that the machine will work properly.
Furthermore, there has also already been proposed in connection with other conventional huskers to so construct the decorticating rollers and the mounting means thereof that the rollers can be easily replaced. Thus, as disclosed, for instance, in the German published patent application DT-OS No. 26 12 349, each of the decorticating rollers may consist of two parts which are detachably connected to one another, that is, of a hub body which is mounted on the driven shaft of the respective decorticating roller for transrotation therewith, and a cylindrical jacket which is provided with the elastic decorticating layer at its outer circumference. Thus, after a substantial wear of the decorticating layer, it is merely necessary to remove the cylindrical jacket together with the worn decorticating layer thereof, and to substitute a new jacket therefor, while the hub body can remain on the shaft thereof without any positional or other change thereof.